The present invention relates generally to the recording of video signals, and more particularly to the recording of time division multiplexed video signals onto analog magnetic tape.
As is well known to those skilled in the art, NTSC and PAL composite television signals are recorded using frequency modulation of the luminance component, which is then used as the AC bias signal for downconverted QAM encoded chrominance components. QAM, or Quadrature Amplitude Modulation encoding, is the suppressed carrier amplitude modulation of two subcarriers in quadrature, such as I and Q for NTSC, or U and V for PAL. U and V chrominance signals are also used in SECAM composite television systems, which use an FM encoded chrominance technique. The signal parameters of these and other composite television standards can be found in "Report 624-4, Characteristics of Television Systems," Reports of the CCIR, 1990, pp. 1-33.
Common consumer VCR standards are VHS, S-VHS, Video-8, and Hi8. The parameters of VHS are defined in Helical-scan Video Tape Cassette System Using 12.65 mm (0.5 in) Magnetic Tape on Type VHS. IEC Standard 774, First Edition, 1983. The parameters of S-VHS (a proprietary system of JVC) are defined in a paper by Y. Nagaoka, M. Tsurata, and H. Fujiwara entitled "High Performance VTR Based on the S-VHS Format, "IEEE Trans Consumer Electronics, 34(3), Aug. 1988, pp. 560-565. The parameters of Video-8 are defined in Helical-scan Video tape Cassette System using 8 mm Magnetic Tape--Video 8, IEC Standard 843, first edition, 1987. The parameters of Hi8 (a proprietary system of Sony Corporation) are defined in a paper by K. Tsuneki, T. Ezaki, and Y. Kubota entitled "Development of the High-Band 8 mm Video System" IEEE Trans Consumer Electronics, 35(3), Aug. 1989, pp. 436-441.
All four VCR systems described above require a composite television signal input which is processed for recording by separating the baseband luminance and QAM encoded chrominance components. These signals are then further encoded for video recording. The baseband luminance signal is applied to an FM modulator, and the QAM encoded chrominance is down-converted to a lower subcarrier frequency. All of the video recording systems use a frequency division multiplex approach where encoded luminance and chrominance occupy separate well defined bands, with strict requirements as to modulated signal bandwidth.
Artifacts commonly associated with composite television signal encoding are cross-chroma and cross-luma (together generically called cross-color) and smear. Cross-color is caused by crosstalk between luminance and chrominance signals. This problem is often quite severe on synthetic imagery, such as graphics. Smear is caused by excessive delay between different channels, and is corrected through the use of matched analog filters and delay lines. In addition, the QAM encoding technique has an inherently poor dynamic range and signal to noise ratio, resulting in severe limitations on the quality of a recovered signal.
Accordingly, an object of the present invention is to record component video signals onto analog magnetic tape without first generating the associated composite television signals.
Another object of the present invention is to record component video signals onto analog magnetic tape with fewer processing stages to suppress noise and distortion.
Still another object of the present invention is to record component video signals onto analog magnetic tape using time division multiplexing and frequency modulation of the luminance and chrominance signals to increase dynamic range and to further suppress or eliminate noise and distortion of a recorded signal.
Yet another object of the present invention is to record component video signals onto analog magnetic tape avoiding cross-color artifacts associated with composite television signal encoding.
Still another object of the present invention is to use time division multiplex and sample rate conversion techniques to supplant the quadrature amplitude modulation chrominance recording technique.
Yet another object of the present invention is to recover and display time division multiplexed video signals from a prerecorded analog magnetic tape.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.